Add some substance to README

Author: ranjanan

README.md

@@ -1,7 +1,51 @@
 # AMG
 
 [![Build Status](https://travis-ci.org/ranjanan/AMG.jl.svg?branch=master)](https://travis-ci.org/ranjanan/AMG.jl)
-
 [![Coverage Status](https://coveralls.io/repos/ranjanan/AMG.jl/badge.svg?branch=master&service=github)](https://coveralls.io/github/ranjanan/AMG.jl?branch=master)
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 [![codecov.io](http://codecov.io/github/ranjanan/AMG.jl/coverage.svg?branch=master)](http://codecov.io/github/ranjanan/AMG.jl?branch=master)
+
+This package lets you solve sparse linear systems using Algebraic Multigrid (AMG). This works especially well for symmetric positive definite matrices. 
+
+## Usage
+
+```julia
+using AMG
+
+A = poisson(1000) # Creates a sample symmetric positive definite sparse matrix
+ml = ruge_stuben(A) # Construct a Ruge-Stuben solver
+# Multilevel Solver
+# -----------------
+# Operator Complexity: 1.9859906604402935
+# Grid Complexity: 1.99
+# No. of Levels: 8
+# Coarse Solver: AMG.Pinv()
+# Level     Unknowns     NonZeros
+# -----     --------     --------
+#     1         1000         2998 [50.35%]
+#     2          500         1498 [25.16%]
+#     3          250          748 [12.56%]
+#     4          125          373 [ 6.26%]
+#     5           62          184 [ 3.09%]
+#     6           31           91 [ 1.53%]
+#     7           15           43 [ 0.72%]
+#     8            7           19 [ 0.32%]
+
+
+solve(ml, A * ones(1000)) # should return ones(1000)
+```
+
+## Roadmap
+
+This package currently supports: 
+1. Ruge-Stuben Solver
+2. Classical Strength of Connection
+3. Ruge-Stuben C/F splitting
+4. Gauss-Siedel smoothers
+5. V cycle multigrid
+
+In the future, this package will support
+1. SmoothedAggregation Solver
+2. Standard Strength of Conneciton
+3. Other splitting methods (like CLJP)
+4. SOR, Jacobi smoothers
+5. W, F, AMLI cycles